The invention relates to a process of producing an outer joint part formed in a non-chip forming way from a plate metal member and having circumferentially distributed, outwardly formed ball tracks.
DE-AS 25 27 376 shows an inner joint part and an outer joint part produced from a tubular member by radially expanding the original cross-section and by radially upsetting the previously expanded tube end. With this method, the ball tracks in the outer joint part, which are produced to extend as far as the open end of the expanded tubular member, are highly susceptible to cracking.
It is an object of the present invention to produce a process of forming an outer joint part so as to increase the strength of the joint. It is a further object of the invention to reduce the risk of crack formation in the region of the longitudinally extending ball tracks.
According to a first embodiment of the process the objective is achieved by using one or several connected process stages wherein a plate metal bar is formed into a rotary member whose axial end regions are formed so as to differ in cross section from a central portion. In at least one separate process stage the ball tracks are formed in an axial region between the deformed end regions.
In an alternative embodiment, the process comprises in at least one or several connected process stages, a tube is formed into a rotary member whose axial end regions are formed so as to differ from a central portion and in at least one separate process stage, the ball tracks are formed in an axial region between the deformed end regions.
An essential and common feature of the teaching in accordance with the invention consists in the fact that, initially, at both axial ends, forming and/or deforming processes lead to a strengthened region, with the axial tracks subsequently being formed between these strengthened rotationally symmetrical regions. In a preferred embodiment, one of the two ends of the outer joint part is conically tapered and the other one conically expanded, the latter being suitable for comprising an intermediate cylindrical portion which is positioned between two conical portions and to which a convoluted boot may be attached for example.
In order to avoid any kind of crack formation in the material while forming the ball tracks it is advantageous to ensure that in each case, at least one end of the formed ball tracks run into one of the conically deformed end regions. The forming operation preferably includes a conical reduction operation at the one axial end relative to the central portion, especially at the end which is followed by a shaft journal, and that the forming process includes at least one conical expansion stage at the other end relative to the especially cylindrical central portion, i.e. at the opposite open end.
The first embodiment corresponds to a process involving a deep drawing operation in at least one first die involving or utilizing a bar. The second alternative corresponds to a forming operation in a die, involving a rotary member, such as a cylindrical tubular member. An upsetting operation can take place at one end and an expanding operation take place at the other end. A later process stage may take place in a further die where the forming operation according to both alternatives may be the same for forming the ball tracks. The means for the second process stage of forming the ball tracks may preferably comprise a punch consisting of a base member with axial bores partially cutting into the base member and of cylindrical pins with rounded edges positioned therein.
Further details may be identified from the enclosed drawings.